1. Technical Field
The present invention relates to seeded growth of single-crystal Aluminum Nitride (AlN), and more particularly, to an apparatus and method for mounting AlN seeds for relatively large, single-crystal AlN growth by sublimation-recondensation.
2. Background Information
The growth of AlN single crystals using the sublimation-recondensation technique, first developed by Slack and McNelly (G. A. Slack and T. F. McNelly, J. Cryst. Growth 34 (1976) 263; and G. A. Slack and T. F. McNelly, J. Cryst. Growth 42 (1977) 560) is currently recognized as a most promising method to produce large bulk AlN single crystals to be used as substrates for the device (e.g., semiconductor) fabrication industry. In this method, a thermal gradient drives the sublimation of a polycrystalline or powder ceramic AlN starting material and subsequent recondensation at a colder portion of a crucible as a single crystal. Large crystals of AlN exceeding 1 cm in diameter have been grown using this sublimation technique (J. C. Rojo, L. J. Schowalter, R. Gaska, M. Shur, M. A. Khan, J. Yang, and D. D. Koleske, Journal of Crystal Growth 240 (2001) 508). These boules were grown without using a seed. Rather, growth was effected by spontaneous nucleation on the walls of the crucible.
Several seeded crystal growth efforts have been attempted using Silicon Carbide (SiC). See, for example, C. M. Balkas, Z. Sitar, T. Zheleva, L. Bergman, R. Nemanich, R. F. Davis, J. Crystal Growth (1997) 363; L. Liu, D. Zhuang, B. Liu, Y. Shi, J. H. Edgar, S. Rajasingam, M. Kuball, Physica Status Solidi A 188 (2001) 769. Attempts at effecting seeded growth using AlN have been described by R. Schlesser, R. Dalmau, Z. Sitar, in the Journal of Crystal Growth 243 (2002) 216–420. However, to date there have been no reports of successful seeded growth of large AlN boules. Thus, a need exists for a method and apparatus capable of providing seeded growth of large (e.g., greater than 1 cm diameter) AlN boules.